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Revision 1.165 by root, Tue Sep 5 13:07:09 2017 UTC

		1	=head1 NAME
		2
		3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
1	=encoding utf-8	5	=encoding utf-8
2
3	=head1 NAME
4
5	JSON::XS - JSON serialising/deserialising, done correctly and fast
6		6
7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
9		9
10	=head1 SYNOPSIS	10	=head1 SYNOPSIS
…		…
37	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
38	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
39		39
40	Beginning with version 2.0 of the JSON module, when both JSON and	40	Beginning with version 2.0 of the JSON module, when both JSON and
41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be	41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
42	overriden) with no overhead due to emulation (by inheritign constructor	42	overridden) with no overhead due to emulation (by inheriting constructor
43	and methods). If JSON::XS is not available, it will fall back to the	43	and methods). If JSON::XS is not available, it will fall back to the
44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS	44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
45	gives you a portable JSON API that can be fast when you need and doesn't	45	gives you a portable JSON API that can be fast when you need it and
46	require a C compiler when that is a problem.	46	doesn't require a C compiler when that is a problem.
47		47
48	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
49	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
50	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
51	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
52	reports for other reasons.	52	reports for other reasons.
53		53
54	See COMPARISON, below, for a comparison to some other JSON modules.
55
56	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
57	vice versa.	55	vice versa.
58		56
59	=head2 FEATURES	57	=head2 FEATURES
60		58
…		…
65	This module knows how to handle Unicode, documents how and when it does	63	This module knows how to handle Unicode, documents how and when it does
66	so, and even documents what "correct" means.	64	so, and even documents what "correct" means.
67		65
68	=item * round-trip integrity	66	=item * round-trip integrity
69		67
70	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
71	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON and Perl, the deserialised data structure is identical on the Perl
72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	level. (e.g. the string "2.0" doesn't suddenly become "2" just because
73	like a number). There minor I<are> exceptions to this, read the MAPPING	71	it looks like a number). There I<are> minor exceptions to this, read the
74	section below to learn about those.	72	MAPPING section below to learn about those.
75		73
76	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
77		75
78	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
79	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
…		…
84	Compared to other JSON modules and other serialisers such as Storable,	82	Compared to other JSON modules and other serialisers such as Storable,
85	this module usually compares favourably in terms of speed, too.	83	this module usually compares favourably in terms of speed, too.
86		84
87	=item * simple to use	85	=item * simple to use
88		86
89	This module has both a simple functional interface as well as an objetc	87	This module has both a simple functional interface as well as an object
90	oriented interface interface.	88	oriented interface.
91		89
92	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
93		91
94	You can choose between the most compact guaranteed-single-line format	92	You can choose between the most compact guaranteed-single-line format
95	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
96	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
97	Unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
98	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
99		97
100	=back	98	=back
101		99
102	=cut	100	=cut
103		101
104	package JSON::XS;	102	package JSON::XS;
105		103
106	use strict;	104	use common::sense;
107		105
108	our $VERSION = '2.01';	106	our $VERSION = 3.04;
109	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
110		108
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
112
113	sub to_json($) {
114	require Carp;
115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
116	}
117
118	sub from_json($) {
119	require Carp;
120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
121	}
122		110
123	use Exporter;	111	use Exporter;
124	use XSLoader;	112	use XSLoader;
125		113
		114	use Types::Serialiser ();
		115
126	=head1 FUNCTIONAL INTERFACE	116	=head1 FUNCTIONAL INTERFACE
127		117
128	The following convenience methods are provided by this module. They are	118	The following convenience methods are provided by this module. They are
129	exported by default:	119	exported by default:
130		120
…		…
137		127
138	This function call is functionally identical to:	128	This function call is functionally identical to:
139		129
140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	130	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
141		131
142	except being faster.	132	Except being faster.
143		133
144	=item $perl_scalar = decode_json $json_text	134	=item $perl_scalar = decode_json $json_text
145		135
146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	136	The opposite of C<encode_json>: expects a UTF-8 (binary) string and tries
147	to parse that as an UTF-8 encoded JSON text, returning the resulting	137	to parse that as a UTF-8 encoded JSON text, returning the resulting
148	reference. Croaks on error.	138	reference. Croaks on error.
149		139
150	This function call is functionally identical to:	140	This function call is functionally identical to:
151		141
152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	142	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153		143
154	except being faster.	144	Except being faster.
155
156	=item $is_boolean = JSON::XS::is_bool $scalar
157
158	Returns true if the passed scalar represents either JSON::XS::true or
159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
160	and are used to represent JSON C<true> and C<false> values in Perl.
161
162	See MAPPING, below, for more information on how JSON values are mapped to
163	Perl.
164		145
165	=back	146	=back
166		147
167		148
168	=head1 A FEW NOTES ON UNICODE AND PERL	149	=head1 A FEW NOTES ON UNICODE AND PERL
…		…
197		178
198	If you didn't know about that flag, just the better, pretend it doesn't	179	If you didn't know about that flag, just the better, pretend it doesn't
199	exist.	180	exist.
200		181
201	=item 4. A "Unicode String" is simply a string where each character can be	182	=item 4. A "Unicode String" is simply a string where each character can be
202	validly interpreted as a Unicode codepoint.	183	validly interpreted as a Unicode code point.
203		184
204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	185	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
205	Unicode string encoded in UTF-8, giving you a binary string.	186	Unicode string encoded in UTF-8, giving you a binary string.
206		187
207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	188	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
245		226
246	If C<$enable> is false, then the C<encode> method will not escape Unicode	227	If C<$enable> is false, then the C<encode> method will not escape Unicode
247	characters unless required by the JSON syntax or other flags. This results	228	characters unless required by the JSON syntax or other flags. This results
248	in a faster and more compact format.	229	in a faster and more compact format.
249		230
		231	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		232	document.
		233
250	The main use for this flag is to produce JSON texts that can be	234	The main use for this flag is to produce JSON texts that can be
251	transmitted over a 7-bit channel, as the encoded JSON texts will not	235	transmitted over a 7-bit channel, as the encoded JSON texts will not
252	contain any 8 bit characters.	236	contain any 8 bit characters.
253		237
254	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	238	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
265	will not be affected in any way by this flag, as C<decode> by default	249	will not be affected in any way by this flag, as C<decode> by default
266	expects Unicode, which is a strict superset of latin1.	250	expects Unicode, which is a strict superset of latin1.
267		251
268	If C<$enable> is false, then the C<encode> method will not escape Unicode	252	If C<$enable> is false, then the C<encode> method will not escape Unicode
269	characters unless required by the JSON syntax or other flags.	253	characters unless required by the JSON syntax or other flags.
		254
		255	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		256	document.
270		257
271	The main use for this flag is efficiently encoding binary data as JSON	258	The main use for this flag is efficiently encoding binary data as JSON
272	text, as most octets will not be escaped, resulting in a smaller encoded	259	text, as most octets will not be escaped, resulting in a smaller encoded
273	size. The disadvantage is that the resulting JSON text is encoded	260	size. The disadvantage is that the resulting JSON text is encoded
274	in latin1 (and must correctly be treated as such when storing and	261	in latin1 (and must correctly be treated as such when storing and
…		…
283		270
284	=item $enabled = $json->get_utf8	271	=item $enabled = $json->get_utf8
285		272
286	If C<$enable> is true (or missing), then the C<encode> method will encode	273	If C<$enable> is true (or missing), then the C<encode> method will encode
287	the JSON result into UTF-8, as required by many protocols, while the	274	the JSON result into UTF-8, as required by many protocols, while the
288	C<decode> method expects to be handled an UTF-8-encoded string. Please	275	C<decode> method expects to be handed a UTF-8-encoded string. Please
289	note that UTF-8-encoded strings do not contain any characters outside the	276	note that UTF-8-encoded strings do not contain any characters outside the
290	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	277	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
291	versions, enabling this option might enable autodetection of the UTF-16	278	versions, enabling this option might enable autodetection of the UTF-16
292	and UTF-32 encoding families, as described in RFC4627.	279	and UTF-32 encoding families, as described in RFC4627.
293		280
294	If C<$enable> is false, then the C<encode> method will return the JSON	281	If C<$enable> is false, then the C<encode> method will return the JSON
295	string as a (non-encoded) Unicode string, while C<decode> expects thus a	282	string as a (non-encoded) Unicode string, while C<decode> expects thus a
296	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	283	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
297	to be done yourself, e.g. using the Encode module.	284	to be done yourself, e.g. using the Encode module.
		285
		286	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		287	document.
298		288
299	Example, output UTF-16BE-encoded JSON:	289	Example, output UTF-16BE-encoded JSON:
300		290
301	use Encode;	291	use Encode;
302	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	292	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
414	[	404	[
415	1, # this comment not allowed in JSON	405	1, # this comment not allowed in JSON
416	# neither this one...	406	# neither this one...
417	]	407	]
418		408
		409	=item * literal ASCII TAB characters in strings
		410
		411	Literal ASCII TAB characters are now allowed in strings (and treated as
		412	C<\t>).
		413
		414	[
		415	"Hello\tWorld",
		416	"Hello<TAB>World", # literal <TAB> would not normally be allowed
		417	]
		418
419	=back	419	=back
420		420
421	=item $json = $json->canonical ([$enable])	421	=item $json = $json->canonical ([$enable])
422		422
423	=item $enabled = $json->get_canonical	423	=item $enabled = $json->get_canonical
…		…
425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
426	by sorting their keys. This is adding a comparatively high overhead.	426	by sorting their keys. This is adding a comparatively high overhead.
427		427
428	If C<$enable> is false, then the C<encode> method will output key-value	428	If C<$enable> is false, then the C<encode> method will output key-value
429	pairs in the order Perl stores them (which will likely change between runs	429	pairs in the order Perl stores them (which will likely change between runs
430	of the same script).	430	of the same script, and can change even within the same run from 5.18
		431	onwards).
431		432
432	This option is useful if you want the same data structure to be encoded as	433	This option is useful if you want the same data structure to be encoded as
433	the same JSON text (given the same overall settings). If it is disabled,	434	the same JSON text (given the same overall settings). If it is disabled,
434	the same hash might be encoded differently even if contains the same data,	435	the same hash might be encoded differently even if contains the same data,
435	as key-value pairs have no inherent ordering in Perl.	436	as key-value pairs have no inherent ordering in Perl.
436		437
437	This setting has no effect when decoding JSON texts.	438	This setting has no effect when decoding JSON texts.
438		439
		440	This setting has currently no effect on tied hashes.
		441
439	=item $json = $json->allow_nonref ([$enable])	442	=item $json = $json->allow_nonref ([$enable])
440		443
441	=item $enabled = $json->get_allow_nonref	444	=item $enabled = $json->get_allow_nonref
442		445
443	If C<$enable> is true (or missing), then the C<encode> method can convert a	446	If C<$enable> is true (or missing), then the C<encode> method can convert a
…		…
454	resulting in an invalid JSON text:	457	resulting in an invalid JSON text:
455		458
456	JSON::XS->new->allow_nonref->encode ("Hello, World!")	459	JSON::XS->new->allow_nonref->encode ("Hello, World!")
457	=> "Hello, World!"	460	=> "Hello, World!"
458		461
		462	=item $json = $json->allow_unknown ([$enable])
		463
		464	=item $enabled = $json->get_allow_unknown
		465
		466	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		467	exception when it encounters values it cannot represent in JSON (for
		468	example, filehandles) but instead will encode a JSON C<null> value. Note
		469	that blessed objects are not included here and are handled separately by
		470	c<allow_nonref>.
		471
		472	If C<$enable> is false (the default), then C<encode> will throw an
		473	exception when it encounters anything it cannot encode as JSON.
		474
		475	This option does not affect C<decode> in any way, and it is recommended to
		476	leave it off unless you know your communications partner.
		477
459	=item $json = $json->allow_blessed ([$enable])	478	=item $json = $json->allow_blessed ([$enable])
460		479
461	=item $enabled = $json->get_allow_blessed	480	=item $enabled = $json->get_allow_blessed
462		481
		482	See L<OBJECT SERIALISATION> for details.
		483
463	If C<$enable> is true (or missing), then the C<encode> method will not	484	If C<$enable> is true (or missing), then the C<encode> method will not
464	barf when it encounters a blessed reference. Instead, the value of the	485	barf when it encounters a blessed reference that it cannot convert
465	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	486	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
466	disabled or no C<TO_JSON> method found) or a representation of the
467	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
468	encoded. Has no effect on C<decode>.
469		487
470	If C<$enable> is false (the default), then C<encode> will throw an	488	If C<$enable> is false (the default), then C<encode> will throw an
471	exception when it encounters a blessed object.	489	exception when it encounters a blessed object that it cannot convert
		490	otherwise.
		491
		492	This setting has no effect on C<decode>.
472		493
473	=item $json = $json->convert_blessed ([$enable])	494	=item $json = $json->convert_blessed ([$enable])
474		495
475	=item $enabled = $json->get_convert_blessed	496	=item $enabled = $json->get_convert_blessed
		497
		498	See L<OBJECT SERIALISATION> for details.
476		499
477	If C<$enable> is true (or missing), then C<encode>, upon encountering a	500	If C<$enable> is true (or missing), then C<encode>, upon encountering a
478	blessed object, will check for the availability of the C<TO_JSON> method	501	blessed object, will check for the availability of the C<TO_JSON> method
479	on the object's class. If found, it will be called in scalar context	502	on the object's class. If found, it will be called in scalar context and
480	and the resulting scalar will be encoded instead of the object. If no	503	the resulting scalar will be encoded instead of the object.
481	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
482	to do.
483		504
484	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	505	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
485	returns other blessed objects, those will be handled in the same	506	returns other blessed objects, those will be handled in the same
486	way. C<TO_JSON> must take care of not causing an endless recursion cycle	507	way. C<TO_JSON> must take care of not causing an endless recursion cycle
487	(== crash) in this case. The name of C<TO_JSON> was chosen because other	508	(== crash) in this case. The name of C<TO_JSON> was chosen because other
488	methods called by the Perl core (== not by the user of the object) are	509	methods called by the Perl core (== not by the user of the object) are
489	usually in upper case letters and to avoid collisions with any C<to_json>	510	usually in upper case letters and to avoid collisions with any C<to_json>
490	function or method.	511	function or method.
491		512
492	This setting does not yet influence C<decode> in any way, but in the	513	If C<$enable> is false (the default), then C<encode> will not consider
493	future, global hooks might get installed that influence C<decode> and are	514	this type of conversion.
494	enabled by this setting.
495		515
496	If C<$enable> is false, then the C<allow_blessed> setting will decide what	516	This setting has no effect on C<decode>.
497	to do when a blessed object is found.	517
		518	=item $json = $json->allow_tags ([$enable])
		519
		520	=item $enabled = $json->allow_tags
		521
		522	See L<OBJECT SERIALISATION> for details.
		523
		524	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		525	blessed object, will check for the availability of the C<FREEZE> method on
		526	the object's class. If found, it will be used to serialise the object into
		527	a nonstandard tagged JSON value (that JSON decoders cannot decode).
		528
		529	It also causes C<decode> to parse such tagged JSON values and deserialise
		530	them via a call to the C<THAW> method.
		531
		532	If C<$enable> is false (the default), then C<encode> will not consider
		533	this type of conversion, and tagged JSON values will cause a parse error
		534	in C<decode>, as if tags were not part of the grammar.
498		535
499	=item $json = $json->filter_json_object ([$coderef->($hashref)])	536	=item $json = $json->filter_json_object ([$coderef->($hashref)])
500		537
501	When C<$coderef> is specified, it will be called from C<decode> each	538	When C<$coderef> is specified, it will be called from C<decode> each
502	time it decodes a JSON object. The only argument is a reference to the	539	time it decodes a JSON object. The only argument is a reference to the
…		…
603	=item $json = $json->max_depth ([$maximum_nesting_depth])	640	=item $json = $json->max_depth ([$maximum_nesting_depth])
604		641
605	=item $max_depth = $json->get_max_depth	642	=item $max_depth = $json->get_max_depth
606		643
607	Sets the maximum nesting level (default C<512>) accepted while encoding	644	Sets the maximum nesting level (default C<512>) accepted while encoding
608	or decoding. If the JSON text or Perl data structure has an equal or	645	or decoding. If a higher nesting level is detected in JSON text or a Perl
609	higher nesting level then this limit, then the encoder and decoder will	646	data structure, then the encoder and decoder will stop and croak at that
610	stop and croak at that point.	647	point.
611		648
612	Nesting level is defined by number of hash- or arrayrefs that the encoder	649	Nesting level is defined by number of hash- or arrayrefs that the encoder
613	needs to traverse to reach a given point or the number of C<{> or C<[>	650	needs to traverse to reach a given point or the number of C<{> or C<[>
614	characters without their matching closing parenthesis crossed to reach a	651	characters without their matching closing parenthesis crossed to reach a
615	given character in a string.	652	given character in a string.
616		653
617	Setting the maximum depth to one disallows any nesting, so that ensures	654	Setting the maximum depth to one disallows any nesting, so that ensures
618	that the object is only a single hash/object or array.	655	that the object is only a single hash/object or array.
619		656
620	The argument to C<max_depth> will be rounded up to the next highest power
621	of two. If no argument is given, the highest possible setting will be	657	If no argument is given, the highest possible setting will be used, which
622	used, which is rarely useful.	658	is rarely useful.
		659
		660	Note that nesting is implemented by recursion in C. The default value has
		661	been chosen to be as large as typical operating systems allow without
		662	crashing.
623		663
624	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	664	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
625		665
626	=item $json = $json->max_size ([$maximum_string_size])	666	=item $json = $json->max_size ([$maximum_string_size])
627		667
628	=item $max_size = $json->get_max_size	668	=item $max_size = $json->get_max_size
629		669
630	Set the maximum length a JSON text may have (in bytes) where decoding is	670	Set the maximum length a JSON text may have (in bytes) where decoding is
631	being attempted. The default is C<0>, meaning no limit. When C<decode>	671	being attempted. The default is C<0>, meaning no limit. When C<decode>
632	is called on a string longer then this number of characters it will not	672	is called on a string that is longer then this many bytes, it will not
633	attempt to decode the string but throw an exception. This setting has no	673	attempt to decode the string but throw an exception. This setting has no
634	effect on C<encode> (yet).	674	effect on C<encode> (yet).
635		675
636	The argument to C<max_size> will be rounded up to the next B<highest>	676	If no argument is given, the limit check will be deactivated (same as when
637	power of two (so may be more than requested). If no argument is given, the	677	C<0> is specified).
638	limit check will be deactivated (same as when C<0> is specified).
639		678
640	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	679	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
641		680
642	=item $json_text = $json->encode ($perl_scalar)	681	=item $json_text = $json->encode ($perl_scalar)
643		682
644	Converts the given Perl data structure (a simple scalar or a reference	683	Converts the given Perl value or data structure to its JSON
645	to a hash or array) to its JSON representation. Simple scalars will be	684	representation. Croaks on error.
646	converted into JSON string or number sequences, while references to arrays
647	become JSON arrays and references to hashes become JSON objects. Undefined
648	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
649	nor C<false> values will be generated.
650		685
651	=item $perl_scalar = $json->decode ($json_text)	686	=item $perl_scalar = $json->decode ($json_text)
652		687
653	The opposite of C<encode>: expects a JSON text and tries to parse it,	688	The opposite of C<encode>: expects a JSON text and tries to parse it,
654	returning the resulting simple scalar or reference. Croaks on error.	689	returning the resulting simple scalar or reference. Croaks on error.
655
656	JSON numbers and strings become simple Perl scalars. JSON arrays become
657	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
658	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
659		690
660	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	691	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
661		692
662	This works like the C<decode> method, but instead of raising an exception	693	This works like the C<decode> method, but instead of raising an exception
663	when there is trailing garbage after the first JSON object, it will	694	when there is trailing garbage after the first JSON object, it will
664	silently stop parsing there and return the number of characters consumed	695	silently stop parsing there and return the number of characters consumed
665	so far.	696	so far.
666		697
667	This is useful if your JSON texts are not delimited by an outer protocol	698	This is useful if your JSON texts are not delimited by an outer protocol
668	(which is not the brightest thing to do in the first place) and you need
669	to know where the JSON text ends.	699	and you need to know where the JSON text ends.
670		700
671	JSON::XS->new->decode_prefix ("[1] the tail")	701	JSON::XS->new->decode_prefix ("[1] the tail")
672	=> ([], 3)	702	=> ([1], 3)
673		703
674	=back	704	=back
		705
		706
		707	=head1 INCREMENTAL PARSING
		708
		709	In some cases, there is the need for incremental parsing of JSON
		710	texts. While this module always has to keep both JSON text and resulting
		711	Perl data structure in memory at one time, it does allow you to parse a
		712	JSON stream incrementally. It does so by accumulating text until it has
		713	a full JSON object, which it then can decode. This process is similar to
		714	using C<decode_prefix> to see if a full JSON object is available, but
		715	is much more efficient (and can be implemented with a minimum of method
		716	calls).
		717
		718	JSON::XS will only attempt to parse the JSON text once it is sure it
		719	has enough text to get a decisive result, using a very simple but
		720	truly incremental parser. This means that it sometimes won't stop as
		721	early as the full parser, for example, it doesn't detect mismatched
		722	parentheses. The only thing it guarantees is that it starts decoding as
		723	soon as a syntactically valid JSON text has been seen. This means you need
		724	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		725	parsing in the presence if syntax errors.
		726
		727	The following methods implement this incremental parser.
		728
		729	=over 4
		730
		731	=item [void, scalar or list context] = $json->incr_parse ([$string])
		732
		733	This is the central parsing function. It can both append new text and
		734	extract objects from the stream accumulated so far (both of these
		735	functions are optional).
		736
		737	If C<$string> is given, then this string is appended to the already
		738	existing JSON fragment stored in the C<$json> object.
		739
		740	After that, if the function is called in void context, it will simply
		741	return without doing anything further. This can be used to add more text
		742	in as many chunks as you want.
		743
		744	If the method is called in scalar context, then it will try to extract
		745	exactly I<one> JSON object. If that is successful, it will return this
		746	object, otherwise it will return C<undef>. If there is a parse error,
		747	this method will croak just as C<decode> would do (one can then use
		748	C<incr_skip> to skip the erroneous part). This is the most common way of
		749	using the method.
		750
		751	And finally, in list context, it will try to extract as many objects
		752	from the stream as it can find and return them, or the empty list
		753	otherwise. For this to work, there must be no separators (other than
		754	whitespace) between the JSON objects or arrays, instead they must be
		755	concatenated back-to-back. If an error occurs, an exception will be
		756	raised as in the scalar context case. Note that in this case, any
		757	previously-parsed JSON texts will be lost.
		758
		759	Example: Parse some JSON arrays/objects in a given string and return
		760	them.
		761
		762	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		763
		764	=item $lvalue_string = $json->incr_text
		765
		766	This method returns the currently stored JSON fragment as an lvalue, that
		767	is, you can manipulate it. This I<only> works when a preceding call to
		768	C<incr_parse> in I<scalar context> successfully returned an object. Under
		769	all other circumstances you must not call this function (I mean it.
		770	although in simple tests it might actually work, it I<will> fail under
		771	real world conditions). As a special exception, you can also call this
		772	method before having parsed anything.
		773
		774	That means you can only use this function to look at or manipulate text
		775	before or after complete JSON objects, not while the parser is in the
		776	middle of parsing a JSON object.
		777
		778	This function is useful in two cases: a) finding the trailing text after a
		779	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		780	(such as commas).
		781
		782	=item $json->incr_skip
		783
		784	This will reset the state of the incremental parser and will remove
		785	the parsed text from the input buffer so far. This is useful after
		786	C<incr_parse> died, in which case the input buffer and incremental parser
		787	state is left unchanged, to skip the text parsed so far and to reset the
		788	parse state.
		789
		790	The difference to C<incr_reset> is that only text until the parse error
		791	occurred is removed.
		792
		793	=item $json->incr_reset
		794
		795	This completely resets the incremental parser, that is, after this call,
		796	it will be as if the parser had never parsed anything.
		797
		798	This is useful if you want to repeatedly parse JSON objects and want to
		799	ignore any trailing data, which means you have to reset the parser after
		800	each successful decode.
		801
		802	=back
		803
		804	=head2 LIMITATIONS
		805
		806	All options that affect decoding are supported, except
		807	C<allow_nonref>. The reason for this is that it cannot be made to work
		808	sensibly: JSON objects and arrays are self-delimited, i.e. you can
		809	concatenate them back to back and still decode them perfectly. This does
		810	not hold true for JSON numbers, however.
		811
		812	For example, is the string C<1> a single JSON number, or is it simply the
		813	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		814	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		815	takes the conservative route and disallows this case.
		816
		817	=head2 EXAMPLES
		818
		819	Some examples will make all this clearer. First, a simple example that
		820	works similarly to C<decode_prefix>: We want to decode the JSON object at
		821	the start of a string and identify the portion after the JSON object:
		822
		823	my $text = "[1,2,3] hello";
		824
		825	my $json = new JSON::XS;
		826
		827	my $obj = $json->incr_parse ($text)
		828	or die "expected JSON object or array at beginning of string";
		829
		830	my $tail = $json->incr_text;
		831	# $tail now contains " hello"
		832
		833	Easy, isn't it?
		834
		835	Now for a more complicated example: Imagine a hypothetical protocol where
		836	you read some requests from a TCP stream, and each request is a JSON
		837	array, without any separation between them (in fact, it is often useful to
		838	use newlines as "separators", as these get interpreted as whitespace at
		839	the start of the JSON text, which makes it possible to test said protocol
		840	with C<telnet>...).
		841
		842	Here is how you'd do it (it is trivial to write this in an event-based
		843	manner):
		844
		845	my $json = new JSON::XS;
		846
		847	# read some data from the socket
		848	while (sysread $socket, my $buf, 4096) {
		849
		850	# split and decode as many requests as possible
		851	for my $request ($json->incr_parse ($buf)) {
		852	# act on the $request
		853	}
		854	}
		855
		856	Another complicated example: Assume you have a string with JSON objects
		857	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		858	[3]>). To parse them, we have to skip the commas between the JSON texts,
		859	and here is where the lvalue-ness of C<incr_text> comes in useful:
		860
		861	my $text = "[1],[2], [3]";
		862	my $json = new JSON::XS;
		863
		864	# void context, so no parsing done
		865	$json->incr_parse ($text);
		866
		867	# now extract as many objects as possible. note the
		868	# use of scalar context so incr_text can be called.
		869	while (my $obj = $json->incr_parse) {
		870	# do something with $obj
		871
		872	# now skip the optional comma
		873	$json->incr_text =~ s/^ \s* , //x;
		874	}
		875
		876	Now lets go for a very complex example: Assume that you have a gigantic
		877	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		878	but you cannot load it into memory fully (this has actually happened in
		879	the real world :).
		880
		881	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		882	can still help you: You implement a (very simple) array parser and let
		883	JSON decode the array elements, which are all full JSON objects on their
		884	own (this wouldn't work if the array elements could be JSON numbers, for
		885	example):
		886
		887	my $json = new JSON::XS;
		888
		889	# open the monster
		890	open my $fh, "<bigfile.json"
		891	or die "bigfile: $!";
		892
		893	# first parse the initial "["
		894	for (;;) {
		895	sysread $fh, my $buf, 65536
		896	or die "read error: $!";
		897	$json->incr_parse ($buf); # void context, so no parsing
		898
		899	# Exit the loop once we found and removed(!) the initial "[".
		900	# In essence, we are (ab-)using the $json object as a simple scalar
		901	# we append data to.
		902	last if $json->incr_text =~ s/^ \s* \[ //x;
		903	}
		904
		905	# now we have the skipped the initial "[", so continue
		906	# parsing all the elements.
		907	for (;;) {
		908	# in this loop we read data until we got a single JSON object
		909	for (;;) {
		910	if (my $obj = $json->incr_parse) {
		911	# do something with $obj
		912	last;
		913	}
		914
		915	# add more data
		916	sysread $fh, my $buf, 65536
		917	or die "read error: $!";
		918	$json->incr_parse ($buf); # void context, so no parsing
		919	}
		920
		921	# in this loop we read data until we either found and parsed the
		922	# separating "," between elements, or the final "]"
		923	for (;;) {
		924	# first skip whitespace
		925	$json->incr_text =~ s/^\s*//;
		926
		927	# if we find "]", we are done
		928	if ($json->incr_text =~ s/^\]//) {
		929	print "finished.\n";
		930	exit;
		931	}
		932
		933	# if we find ",", we can continue with the next element
		934	if ($json->incr_text =~ s/^,//) {
		935	last;
		936	}
		937
		938	# if we find anything else, we have a parse error!
		939	if (length $json->incr_text) {
		940	die "parse error near ", $json->incr_text;
		941	}
		942
		943	# else add more data
		944	sysread $fh, my $buf, 65536
		945	or die "read error: $!";
		946	$json->incr_parse ($buf); # void context, so no parsing
		947	}
		948
		949	This is a complex example, but most of the complexity comes from the fact
		950	that we are trying to be correct (bear with me if I am wrong, I never ran
		951	the above example :).
		952
675		953
676		954
677	=head1 MAPPING	955	=head1 MAPPING
678		956
679	This section describes how JSON::XS maps Perl values to JSON values and	957	This section describes how JSON::XS maps Perl values to JSON values and
…		…
716	If the number consists of digits only, JSON::XS will try to represent	994	If the number consists of digits only, JSON::XS will try to represent
717	it as an integer value. If that fails, it will try to represent it as	995	it as an integer value. If that fails, it will try to represent it as
718	a numeric (floating point) value if that is possible without loss of	996	a numeric (floating point) value if that is possible without loss of
719	precision. Otherwise it will preserve the number as a string value (in	997	precision. Otherwise it will preserve the number as a string value (in
720	which case you lose roundtripping ability, as the JSON number will be	998	which case you lose roundtripping ability, as the JSON number will be
721	re-encoded toa JSON string).	999	re-encoded to a JSON string).
722		1000
723	Numbers containing a fractional or exponential part will always be	1001	Numbers containing a fractional or exponential part will always be
724	represented as numeric (floating point) values, possibly at a loss of	1002	represented as numeric (floating point) values, possibly at a loss of
725	precision (in which case you might lose perfect roundtripping ability, but	1003	precision (in which case you might lose perfect roundtripping ability, but
726	the JSON number will still be re-encoded as a JSON number).	1004	the JSON number will still be re-encoded as a JSON number).
727		1005
		1006	Note that precision is not accuracy - binary floating point values cannot
		1007	represent most decimal fractions exactly, and when converting from and to
		1008	floating point, JSON::XS only guarantees precision up to but not including
		1009	the least significant bit.
		1010
728	=item true, false	1011	=item true, false
729		1012
730	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1013	These JSON atoms become C<Types::Serialiser::true> and
731	respectively. They are overloaded to act almost exactly like the numbers	1014	C<Types::Serialiser::false>, respectively. They are overloaded to act
732	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using	1015	almost exactly like the numbers C<1> and C<0>. You can check whether
733	the C<JSON::XS::is_bool> function.	1016	a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
		1017	function (after C<use Types::Serialier>, of course).
734		1018
735	=item null	1019	=item null
736		1020
737	A JSON null atom becomes C<undef> in Perl.	1021	A JSON null atom becomes C<undef> in Perl.
		1022
		1023	=item shell-style comments (C<< # I<text> >>)
		1024
		1025	As a nonstandard extension to the JSON syntax that is enabled by the
		1026	C<relaxed> setting, shell-style comments are allowed. They can start
		1027	anywhere outside strings and go till the end of the line.
		1028
		1029	=item tagged values (C<< (I<tag>)I<value> >>).
		1030
		1031	Another nonstandard extension to the JSON syntax, enabled with the
		1032	C<allow_tags> setting, are tagged values. In this implementation, the
		1033	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1034	I<value> must be a JSON array encoding optional constructor arguments.
		1035
		1036	See L<OBJECT SERIALISATION>, below, for details.
738		1037
739	=back	1038	=back
740		1039
741		1040
742	=head2 PERL -> JSON	1041	=head2 PERL -> JSON
…		…
747		1046
748	=over 4	1047	=over 4
749		1048
750	=item hash references	1049	=item hash references
751		1050
752	Perl hash references become JSON objects. As there is no inherent ordering	1051	Perl hash references become JSON objects. As there is no inherent
753	in hash keys (or JSON objects), they will usually be encoded in a	1052	ordering in hash keys (or JSON objects), they will usually be encoded
754	pseudo-random order that can change between runs of the same program but	1053	in a pseudo-random order. JSON::XS can optionally sort the hash keys
755	stays generally the same within a single run of a program. JSON::XS can	1054	(determined by the I<canonical> flag), so the same datastructure will
756	optionally sort the hash keys (determined by the I<canonical> flag), so	1055	serialise to the same JSON text (given same settings and version of
757	the same datastructure will serialise to the same JSON text (given same	1056	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
758	settings and version of JSON::XS), but this incurs a runtime overhead	1057	e.g. when you want to compare some JSON text against another for equality.
759	and is only rarely useful, e.g. when you want to compare some JSON text
760	against another for equality.
761		1058
762	=item array references	1059	=item array references
763		1060
764	Perl array references become JSON arrays.	1061	Perl array references become JSON arrays.
765		1062
766	=item other references	1063	=item other references
767		1064
768	Other unblessed references are generally not allowed and will cause an	1065	Other unblessed references are generally not allowed and will cause an
769	exception to be thrown, except for references to the integers C<0> and	1066	exception to be thrown, except for references to the integers C<0> and
770	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1067	C<1>, which get turned into C<false> and C<true> atoms in JSON.
771	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
772		1068
		1069	Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
		1070	can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
		1071	and C<Types::Serialiser::true> to improve readability.
		1072
		1073	use Types::Serialiser;
773	encode_json [\0,JSON::XS::true] # yields [false,true]	1074	encode_json [\0, Types::Serialiser::true] # yields [false,true]
774		1075
775	=item JSON::XS::true, JSON::XS::false	1076	=item Types::Serialiser::true, Types::Serialiser::false
776		1077
777	These special values become JSON true and JSON false values,	1078	These special values from the L<Types::Serialiser> module become JSON true
778	respectively. You can also use C<\1> and C<\0> directly if you want.	1079	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1080	directly if you want.
779		1081
780	=item blessed objects	1082	=item blessed objects
781		1083
782	Blessed objects are not directly representable in JSON. See the	1084	Blessed objects are not directly representable in JSON, but C<JSON::XS>
783	C<allow_blessed> and C<convert_blessed> methods on various options on	1085	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
784	how to deal with this: basically, you can choose between throwing an	1086	below, for details.
785	exception, encoding the reference as if it weren't blessed, or provide
786	your own serialiser method.
787		1087
788	=item simple scalars	1088	=item simple scalars
789		1089
790	Simple Perl scalars (any scalar that is not a reference) are the most	1090	Simple Perl scalars (any scalar that is not a reference) are the most
791	difficult objects to encode: JSON::XS will encode undefined scalars as	1091	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
816	my $x = "3"; # some variable containing a string	1116	my $x = "3"; # some variable containing a string
817	$x += 0; # numify it, ensuring it will be dumped as a number	1117	$x += 0; # numify it, ensuring it will be dumped as a number
818	$x *= 1; # same thing, the choice is yours.	1118	$x *= 1; # same thing, the choice is yours.
819		1119
820	You can not currently force the type in other, less obscure, ways. Tell me	1120	You can not currently force the type in other, less obscure, ways. Tell me
821	if you need this capability (but don't forget to explain why its needed	1121	if you need this capability (but don't forget to explain why it's needed
822	:).	1122	:).
823		1123
		1124	Note that numerical precision has the same meaning as under Perl (so
		1125	binary to decimal conversion follows the same rules as in Perl, which
		1126	can differ to other languages). Also, your perl interpreter might expose
		1127	extensions to the floating point numbers of your platform, such as
		1128	infinities or NaN's - these cannot be represented in JSON, and it is an
		1129	error to pass those in.
		1130
824	=back	1131	=back
		1132
		1133	=head2 OBJECT SERIALISATION
		1134
		1135	As JSON cannot directly represent Perl objects, you have to choose between
		1136	a pure JSON representation (without the ability to deserialise the object
		1137	automatically again), and a nonstandard extension to the JSON syntax,
		1138	tagged values.
		1139
		1140	=head3 SERIALISATION
		1141
		1142	What happens when C<JSON::XS> encounters a Perl object depends on the
		1143	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1144	used in this order:
		1145
		1146	=over 4
		1147
		1148	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1149
		1150	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1151	serialisation protocol to create a tagged JSON value, using a nonstandard
		1152	extension to the JSON syntax.
		1153
		1154	This works by invoking the C<FREEZE> method on the object, with the first
		1155	argument being the object to serialise, and the second argument being the
		1156	constant string C<JSON> to distinguish it from other serialisers.
		1157
		1158	The C<FREEZE> method can return any number of values (i.e. zero or
		1159	more). These values and the paclkage/classname of the object will then be
		1160	encoded as a tagged JSON value in the following format:
		1161
		1162	("classname")[FREEZE return values...]
		1163
		1164	e.g.:
		1165
		1166	("URI")["http://www.google.com/"]
		1167	("MyDate")[2013,10,29]
		1168	("ImageData::JPEG")["Z3...VlCg=="]
		1169
		1170	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1171	objects C<type> and C<id> members to encode the object:
		1172
		1173	sub My::Object::FREEZE {
		1174	my ($self, $serialiser) = @_;
		1175
		1176	($self->{type}, $self->{id})
		1177	}
		1178
		1179	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1180
		1181	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1182	context. It must return a single scalar that can be directly encoded into
		1183	JSON. This scalar replaces the object in the JSON text.
		1184
		1185	For example, the following C<TO_JSON> method will convert all L<URI>
		1186	objects to JSON strings when serialised. The fatc that these values
		1187	originally were L<URI> objects is lost.
		1188
		1189	sub URI::TO_JSON {
		1190	my ($uri) = @_;
		1191	$uri->as_string
		1192	}
		1193
		1194	=item 3. C<allow_blessed> is enabled.
		1195
		1196	The object will be serialised as a JSON null value.
		1197
		1198	=item 4. none of the above
		1199
		1200	If none of the settings are enabled or the respective methods are missing,
		1201	C<JSON::XS> throws an exception.
		1202
		1203	=back
		1204
		1205	=head3 DESERIALISATION
		1206
		1207	For deserialisation there are only two cases to consider: either
		1208	nonstandard tagging was used, in which case C<allow_tags> decides,
		1209	or objects cannot be automatically be deserialised, in which
		1210	case you can use postprocessing or the C<filter_json_object> or
		1211	C<filter_json_single_key_object> callbacks to get some real objects our of
		1212	your JSON.
		1213
		1214	This section only considers the tagged value case: I a tagged JSON object
		1215	is encountered during decoding and C<allow_tags> is disabled, a parse
		1216	error will result (as if tagged values were not part of the grammar).
		1217
		1218	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1219	of the package/classname used during serialisation (it will not attempt
		1220	to load the package as a Perl module). If there is no such method, the
		1221	decoding will fail with an error.
		1222
		1223	Otherwise, the C<THAW> method is invoked with the classname as first
		1224	argument, the constant string C<JSON> as second argument, and all the
		1225	values from the JSON array (the values originally returned by the
		1226	C<FREEZE> method) as remaining arguments.
		1227
		1228	The method must then return the object. While technically you can return
		1229	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1230	make that work in all cases, so better return an actual blessed reference.
		1231
		1232	As an example, let's implement a C<THAW> function that regenerates the
		1233	C<My::Object> from the C<FREEZE> example earlier:
		1234
		1235	sub My::Object::THAW {
		1236	my ($class, $serialiser, $type, $id) = @_;
		1237
		1238	$class->new (type => $type, id => $id)
		1239	}
825		1240
826		1241
827	=head1 ENCODING/CODESET FLAG NOTES	1242	=head1 ENCODING/CODESET FLAG NOTES
828		1243
829	The interested reader might have seen a number of flags that signify	1244	The interested reader might have seen a number of flags that signify
830	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be	1245	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
831	some confusion on what these do, so here is a short comparison:	1246	some confusion on what these do, so here is a short comparison:
832		1247
833	C<utf8> controls wether the JSON text created by C<encode> (and expected	1248	C<utf8> controls whether the JSON text created by C<encode> (and expected
834	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only	1249	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
835	control wether C<encode> escapes character values outside their respective	1250	control whether C<encode> escapes character values outside their respective
836	codeset range. Neither of these flags conflict with each other, although	1251	codeset range. Neither of these flags conflict with each other, although
837	some combinations make less sense than others.	1252	some combinations make less sense than others.
838		1253
839	Care has been taken to make all flags symmetrical with respect to	1254	Care has been taken to make all flags symmetrical with respect to
840	C<encode> and C<decode>, that is, texts encoded with any combination of	1255	C<encode> and C<decode>, that is, texts encoded with any combination of
…		…
854	=item C<utf8> flag disabled	1269	=item C<utf8> flag disabled
855		1270
856	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1271	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
857	and expect Unicode strings, that is, characters with high ordinal Unicode	1272	and expect Unicode strings, that is, characters with high ordinal Unicode
858	values (> 255) will be encoded as such characters, and likewise such	1273	values (> 255) will be encoded as such characters, and likewise such
859	characters are decoded as-is, no canges to them will be done, except	1274	characters are decoded as-is, no changes to them will be done, except
860	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1275	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
861	respectively (to Perl, these are the same thing in strings unless you do	1276	respectively (to Perl, these are the same thing in strings unless you do
862	funny/weird/dumb stuff).	1277	funny/weird/dumb stuff).
863		1278
864	This is useful when you want to do the encoding yourself (e.g. when you	1279	This is useful when you want to do the encoding yourself (e.g. when you
…		…
874	expect your input strings to be encoded as UTF-8, that is, no "character"	1289	expect your input strings to be encoded as UTF-8, that is, no "character"
875	of the input string must have any value > 255, as UTF-8 does not allow	1290	of the input string must have any value > 255, as UTF-8 does not allow
876	that.	1291	that.
877		1292
878	The C<utf8> flag therefore switches between two modes: disabled means you	1293	The C<utf8> flag therefore switches between two modes: disabled means you
879	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded	1294	will get a Unicode string in Perl, enabled means you get a UTF-8 encoded
880	octet/binary string in Perl.	1295	octet/binary string in Perl.
881		1296
882	=item C<latin1> or C<ascii> flags enabled	1297	=item C<latin1> or C<ascii> flags enabled
883		1298
884	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters	1299	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
…		…
920	proper subset of most 8-bit and multibyte encodings in use in the world.	1335	proper subset of most 8-bit and multibyte encodings in use in the world.
921		1336
922	=back	1337	=back
923		1338
924		1339
925	=head1 COMPARISON	1340	=head2 JSON and ECMAscript
926		1341
927	As already mentioned, this module was created because none of the existing	1342	JSON syntax is based on how literals are represented in javascript (the
928	JSON modules could be made to work correctly. First I will describe the	1343	not-standardised predecessor of ECMAscript) which is presumably why it is
929	problems (or pleasures) I encountered with various existing JSON modules,	1344	called "JavaScript Object Notation".
930	followed by some benchmark values. JSON::XS was designed not to suffer
931	from any of these problems or limitations.
932		1345
933	=over 4	1346	However, JSON is not a subset (and also not a superset of course) of
		1347	ECMAscript (the standard) or javascript (whatever browsers actually
		1348	implement).
934		1349
935	=item JSON 2.xx	1350	If you want to use javascript's C<eval> function to "parse" JSON, you
		1351	might run into parse errors for valid JSON texts, or the resulting data
		1352	structure might not be queryable:
936		1353
937	A marvellous piece of engineering, this module either uses JSON::XS	1354	One of the problems is that U+2028 and U+2029 are valid characters inside
938	directly when available (so will be 100% compatible with it, including	1355	JSON strings, but are not allowed in ECMAscript string literals, so the
939	speed), or it uses JSON::PP, which is basically JSON::XS translated to	1356	following Perl fragment will not output something that can be guaranteed
940	Pure Perl, which should be 100% compatible with JSON::XS, just a bit	1357	to be parsable by javascript's C<eval>:
941	slower.
942		1358
943	You cannot really lose by using this module, especially as it tries very	1359	use JSON::XS;
944	hard to work even with ancient Perl versions, while JSON::XS does not.
945		1360
946	=item JSON 1.07	1361	print encode_json [chr 0x2028];
947		1362
948	Slow (but very portable, as it is written in pure Perl).	1363	The right fix for this is to use a proper JSON parser in your javascript
		1364	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1365	F<json2.js> parser).
949		1366
950	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1367	If this is not an option, you can, as a stop-gap measure, simply encode to
951	undocumented. One can get far by feeding it Unicode strings and doing	1368	ASCII-only JSON:
952	en-/decoding oneself, but Unicode escapes are not working properly).
953		1369
954	No round-tripping (strings get clobbered if they look like numbers, e.g.	1370	use JSON::XS;
955	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
956	decode into the number 2.
957		1371
958	=item JSON::PC 0.01	1372	print JSON::XS->new->ascii->encode ([chr 0x2028]);
959		1373
960	Very fast.	1374	Note that this will enlarge the resulting JSON text quite a bit if you
		1375	have many non-ASCII characters. You might be tempted to run some regexes
		1376	to only escape U+2028 and U+2029, e.g.:
961		1377
962	Undocumented/buggy Unicode handling.	1378	# DO NOT USE THIS!
		1379	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1380	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1381	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1382	print $json;
963		1383
964	No round-tripping.	1384	Note that I<this is a bad idea>: the above only works for U+2028 and
		1385	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1386	javascript implementations, however, have issues with other characters as
		1387	well - using C<eval> naively simply I<will> cause problems.
965		1388
966	Has problems handling many Perl values (e.g. regex results and other magic	1389	Another problem is that some javascript implementations reserve
967	values will make it croak).	1390	some property names for their own purposes (which probably makes
		1391	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1392	C<__proto__> property name for its own purposes.
968		1393
969	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1394	If that is a problem, you could parse try to filter the resulting JSON
970	which is not a valid JSON text.	1395	output for these property strings, e.g.:
971		1396
972	Unmaintained (maintainer unresponsive for many months, bugs are not	1397	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
973	getting fixed).
974		1398
975	=item JSON::Syck 0.21	1399	This works because C<__proto__> is not valid outside of strings, so every
		1400	occurrence of C<"__proto__"\s*:> must be a string used as property name.
976		1401
977	Very buggy (often crashes).	1402	If you know of other incompatibilities, please let me know.
978
979	Very inflexible (no human-readable format supported, format pretty much
980	undocumented. I need at least a format for easy reading by humans and a
981	single-line compact format for use in a protocol, and preferably a way to
982	generate ASCII-only JSON texts).
983
984	Completely broken (and confusingly documented) Unicode handling (Unicode
985	escapes are not working properly, you need to set ImplicitUnicode to
986	I<different> values on en- and decoding to get symmetric behaviour).
987
988	No round-tripping (simple cases work, but this depends on whether the scalar
989	value was used in a numeric context or not).
990
991	Dumping hashes may skip hash values depending on iterator state.
992
993	Unmaintained (maintainer unresponsive for many months, bugs are not
994	getting fixed).
995
996	Does not check input for validity (i.e. will accept non-JSON input and
997	return "something" instead of raising an exception. This is a security
998	issue: imagine two banks transferring money between each other using
999	JSON. One bank might parse a given non-JSON request and deduct money,
1000	while the other might reject the transaction with a syntax error. While a
1001	good protocol will at least recover, that is extra unnecessary work and
1002	the transaction will still not succeed).
1003
1004	=item JSON::DWIW 0.04
1005
1006	Very fast. Very natural. Very nice.
1007
1008	Undocumented Unicode handling (but the best of the pack. Unicode escapes
1009	still don't get parsed properly).
1010
1011	Very inflexible.
1012
1013	No round-tripping.
1014
1015	Does not generate valid JSON texts (key strings are often unquoted, empty keys
1016	result in nothing being output)
1017
1018	Does not check input for validity.
1019
1020	=back
1021		1403
1022		1404
1023	=head2 JSON and YAML	1405	=head2 JSON and YAML
1024		1406
1025	You often hear that JSON is a subset of YAML. This is, however, a mass	1407	You often hear that JSON is a subset of YAML. This is, however, a mass
1026	hysteria(*) and very far from the truth. In general, there is no way to	1408	hysteria(*) and very far from the truth (as of the time of this writing),
		1409	so let me state it clearly: I<in general, there is no way to configure
1027	configure JSON::XS to output a data structure as valid YAML that works for	1410	JSON::XS to output a data structure as valid YAML> that works in all
1028	all cases.	1411	cases.
1029		1412
1030	If you really must use JSON::XS to generate YAML, you should use this	1413	If you really must use JSON::XS to generate YAML, you should use this
1031	algorithm (subject to change in future versions):	1414	algorithm (subject to change in future versions):
1032		1415
1033	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1416	my $to_yaml = JSON::XS->new->utf8->space_after (1);
1034	my $yaml = $to_yaml->encode ($ref) . "\n";	1417	my $yaml = $to_yaml->encode ($ref) . "\n";
1035		1418
1036	This will I<usually> generate JSON texts that also parse as valid	1419	This will I<usually> generate JSON texts that also parse as valid
1037	YAML. Please note that YAML has hardcoded limits on (simple) object key	1420	YAML. Please note that YAML has hardcoded limits on (simple) object key
1038	lengths that JSON doesn't have and also has different and incompatible	1421	lengths that JSON doesn't have and also has different and incompatible
1039	unicode handling, so you should make sure that your hash keys are	1422	unicode character escape syntax, so you should make sure that your hash
1040	noticeably shorter than the 1024 "stream characters" YAML allows and that	1423	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1041	you do not have codepoints with values outside the Unicode BMP (basic	1424	and that you do not have characters with codepoint values outside the
1042	multilingual page). YAML also does not allow C<\/> sequences in strings	1425	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1043	(which JSON::XS does not I<currently> generate).	1426	sequences in strings (which JSON::XS does not I<currently> generate, but
		1427	other JSON generators might).
1044		1428
1045	There might be other incompatibilities that I am not aware of (or the YAML	1429	There might be other incompatibilities that I am not aware of (or the YAML
1046	specification has been changed yet again - it does so quite often). In	1430	specification has been changed yet again - it does so quite often). In
1047	general you should not try to generate YAML with a JSON generator or vice	1431	general you should not try to generate YAML with a JSON generator or vice
1048	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1432	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1051		1435
1052	=over 4	1436	=over 4
1053		1437
1054	=item (*)	1438	=item (*)
1055		1439
1056	This is spread actively by the YAML team, however. For many years now they	1440	I have been pressured multiple times by Brian Ingerson (one of the
1057	claim YAML were a superset of JSON, even when proven otherwise.	1441	authors of the YAML specification) to remove this paragraph, despite him
		1442	acknowledging that the actual incompatibilities exist. As I was personally
		1443	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1444	educate people about these issues, so others do not run into the same
		1445	problem again and again. After this, Brian called me a (quote)I<complete
		1446	and worthless idiot>(unquote).
1058		1447
1059	Even the author of this manpage was at some point accused of providing	1448	In my opinion, instead of pressuring and insulting people who actually
1060	"incorrect" information, despite the evidence presented (claims ranged	1449	clarify issues with YAML and the wrong statements of some of its
1061	from "your documentation contains inaccurate and negative statements about	1450	proponents, I would kindly suggest reading the JSON spec (which is not
1062	YAML" (the only negative comment is this footnote, and it didn't exist	1451	that difficult or long) and finally make YAML compatible to it, and
1063	back then; the question on which claims were inaccurate was never answered	1452	educating users about the changes, instead of spreading lies about the
1064	etc.) to "the YAML spec is not up-to-date" (the *real* and supposedly	1453	real compatibility for many I<years> and trying to silence people who
1065	JSON-compatible spec is apparently not currently publicly available)	1454	point out that it isn't true.
1066	to actual requests to replace this section by *incorrect* information,
1067	suppressing information about the real problem).
1068		1455
1069	So whenever you are told that YAML was a superset of JSON, first check	1456	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
1070	wether it is really true (it might be when you check it, but it certainly	1457	though the incompatibilities have been documented (and are known to Brian)
1071	was not true when this was written). I would much prefer if the YAML team	1458	for many years and the spec makes explicit claims that YAML is a superset
1072	would spent their time on actually making JSON compatibility a truth	1459	of JSON. It would be so easy to fix, but apparently, bullying people and
1073	(JSON, after all, has a very small and simple specification) instead of	1460	corrupting userdata is so much easier.
1074	trying to lobby/force people into reporting untruths.
1075		1461
1076	=back	1462	=back
1077		1463
1078		1464
1079	=head2 SPEED	1465	=head2 SPEED
…		…
1083	in the JSON::XS distribution, to make it easy to compare on your own	1469	in the JSON::XS distribution, to make it easy to compare on your own
1084	system.	1470	system.
1085		1471
1086	First comes a comparison between various modules using	1472	First comes a comparison between various modules using
1087	a very short single-line JSON string (also available at	1473	a very short single-line JSON string (also available at
1088	L<http://dist.schmorp.de/misc/json/long.json>).	1474	L<http://dist.schmorp.de/misc/json/short.json>).
1089		1475
1090	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1476	{"method": "handleMessage", "params": ["user1",
1091	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1477	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1478	1, 0]}
1092		1479
1093	It shows the number of encodes/decodes per second (JSON::XS uses	1480	It shows the number of encodes/decodes per second (JSON::XS uses
1094	the functional interface, while JSON::XS/2 uses the OO interface	1481	the functional interface, while JSON::XS/2 uses the OO interface
1095	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1482	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1096	shrink). Higher is better:	1483	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1484	uses the from_json method). Higher is better:
1097		1485
1098	module | encode | decode |	1486	module | encode | decode |
1099	-----------|------------|------------|	1487	--------------|------------|------------|
1100	JSON 1.x | 4990.842 | 4088.813 |	1488	JSON::DWIW/DS | 86302.551 | 102300.098 |
1101	JSON::DWIW | 51653.990 | 71575.154 |	1489	JSON::DWIW/FJ | 86302.551 | 75983.768 |
1102	JSON::PC | 65948.176 | 74631.744 |	1490	JSON::PP | 15827.562 | 6638.658 |
1103	JSON::PP | 8931.652 | 3817.168 |	1491	JSON::Syck | 63358.066 | 47662.545 |
1104	JSON::Syck | 24877.248 | 27776.848 |	1492	JSON::XS | 511500.488 | 511500.488 |
1105	JSON::XS | 388361.481 | 227951.304 |	1493	JSON::XS/2 | 291271.111 | 388361.481 |
1106	JSON::XS/2 | 227951.304 | 218453.333 |	1494	JSON::XS/3 | 361577.931 | 361577.931 |
1107	JSON::XS/3 | 338250.323 | 218453.333 |	1495	Storable | 66788.280 | 265462.278 |
1108	Storable | 16500.016 | 135300.129 |
1109	-----------+------------+------------+	1496	--------------+------------+------------+
1110		1497
1111	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1498	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1112	about three times faster on decoding, and over forty times faster	1499	about five times faster on decoding, and over thirty to seventy times
1113	than JSON, even with pretty-printing and key sorting. It also compares	1500	faster than JSON's pure perl implementation. It also compares favourably
1114	favourably to Storable for small amounts of data.	1501	to Storable for small amounts of data.
1115		1502
1116	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1503	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1117	search API (L>http://dist.schmorp.de/misc/json/long.json>).	1504	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1118		1505
1119	module | encode | decode |	1506	module | encode | decode |
1120	-----------|------------|------------|	1507	--------------|------------|------------|
1121	JSON 1.x | 55.260 | 34.971 |	1508	JSON::DWIW/DS | 1647.927 | 2673.916 |
1122	JSON::DWIW | 825.228 | 1082.513 |	1509	JSON::DWIW/FJ | 1630.249 | 2596.128 |
1123	JSON::PC | 3571.444 | 2394.829 |
1124	JSON::PP | 210.987 | 32.574 |	1510	JSON::PP | 400.640 | 62.311 |
1125	JSON::Syck | 552.551 | 787.544 |	1511	JSON::Syck | 1481.040 | 1524.869 |
1126	JSON::XS | 5780.463 | 4854.519 |	1512	JSON::XS | 20661.596 | 9541.183 |
1127	JSON::XS/2 | 3869.998 | 4798.975 |	1513	JSON::XS/2 | 10683.403 | 9416.938 |
1128	JSON::XS/3 | 5862.880 | 4798.975 |	1514	JSON::XS/3 | 20661.596 | 9400.054 |
1129	Storable | 4445.002 | 5235.027 |	1515	Storable | 19765.806 | 10000.725 |
1130	-----------+------------+------------+	1516	--------------+------------+------------+
1131		1517
1132	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1518	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1133	decodes faster).	1519	decodes a bit faster).
1134		1520
1135	On large strings containing lots of high Unicode characters, some modules	1521	On large strings containing lots of high Unicode characters, some modules
1136	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1522	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1137	will be broken due to missing (or wrong) Unicode handling. Others refuse	1523	will be broken due to missing (or wrong) Unicode handling. Others refuse
1138	to decode or encode properly, so it was impossible to prepare a fair	1524	to decode or encode properly, so it was impossible to prepare a fair
…		…
1174	information you might want to make sure that exceptions thrown by JSON::XS	1560	information you might want to make sure that exceptions thrown by JSON::XS
1175	will not end up in front of untrusted eyes.	1561	will not end up in front of untrusted eyes.
1176		1562
1177	If you are using JSON::XS to return packets to consumption	1563	If you are using JSON::XS to return packets to consumption
1178	by JavaScript scripts in a browser you should have a look at	1564	by JavaScript scripts in a browser you should have a look at
1179	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1565	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1180	you are vulnerable to some common attack vectors (which really are browser	1566	see whether you are vulnerable to some common attack vectors (which really
1181	design bugs, but it is still you who will have to deal with it, as major	1567	are browser design bugs, but it is still you who will have to deal with
1182	browser developers care only for features, not about getting security	1568	it, as major browser developers care only for features, not about getting
1183	right).	1569	security right).
1184		1570
1185		1571
		1572	=head1 "OLD" VS. "NEW" JSON (RFC 4627 VS. RFC 7159)
		1573
		1574	TL;DR: Due to security concerns, JSON::XS will not allow scalar data in
		1575	JSON texts by default - you need to create your own JSON::XS object and
		1576	enable C<allow_nonref>:
		1577
		1578
		1579	my $json = JSON::XS->new->allow_nonref;
		1580
		1581	$text = $json->encode ($data);
		1582	$data = $json->decode ($text);
		1583
		1584	The long version: JSON being an important and supposedly stable format,
		1585	the IETF standardised it as RFC 4627 in 2006. Unfortunately, the inventor
		1586	of JSON, Dougles Crockford, unilaterally changed the definition of JSON in
		1587	javascript. Rather than create a fork, the IETF decided to standardise the
		1588	new syntax (apparently, so Iw as told, without finding it very amusing).
		1589
		1590	The biggest difference between thed original JSON and the new JSON is that
		1591	the new JSON supports scalars (anything other than arrays and objects) at
		1592	the toplevel of a JSON text. While this is strictly backwards compatible
		1593	to older versions, it breaks a number of protocols that relied on sending
		1594	JSON back-to-back, and is a minor security concern.
		1595
		1596	For example, imagine you have two banks communicating, and on one side,
		1597	trhe JSON coder gets upgraded. Two messages, such as C<10> and C<1000>
		1598	might then be confused to mean C<101000>, something that couldn't happen
		1599	in the original JSON, because niether of these messages would be valid
		1600	JSON.
		1601
		1602	If one side accepts these messages, then an upgrade in the coder on either
		1603	side could result in this becoming exploitable.
		1604
		1605	This module has always allowed these messages as an optional extension, by
		1606	default disabled. The security concerns are the reason why the default is
		1607	still disabled, but future versions might/will likely upgrade to the newer
		1608	RFC as default format, so you are advised to check your implementation
		1609	and/or override the default with C<< ->allow_nonref (0) >> to ensure that
		1610	future versions are safe.
		1611
		1612
		1613	=head1 INTEROPERABILITY WITH OTHER MODULES
		1614
		1615	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1616	constants. That means that the JSON true and false values will be
		1617	comaptible to true and false values of other modules that do the same,
		1618	such as L<JSON::PP> and L<CBOR::XS>.
		1619
		1620
		1621	=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
		1622
		1623	As long as you only serialise data that can be directly expressed in JSON,
		1624	C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
		1625	but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
		1626	than the official JSON testsuite has found in C<JSON::XS> (0)).
		1627
		1628	When you have trouble decoding JSON generated by this module using other
		1629	decoders, then it is very likely that you have an encoding mismatch or the
		1630	other decoder is broken.
		1631
		1632	When decoding, C<JSON::XS> is strict by default and will likely catch all
		1633	errors. There are currently two settings that change this: C<relaxed>
		1634	makes C<JSON::XS> accept (but not generate) some non-standard extensions,
		1635	and C<allow_tags> will allow you to encode and decode Perl objects, at the
		1636	cost of not outputting valid JSON anymore.
		1637
		1638	=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1639
		1640	When you use C<allow_tags> to use the extended (and also nonstandard and
		1641	invalid) JSON syntax for serialised objects, and you still want to decode
		1642	the generated When you want to serialise objects, you can run a regex
		1643	to replace the tagged syntax by standard JSON arrays (it only works for
		1644	"normal" package names without comma, newlines or single colons). First,
		1645	the readable Perl version:
		1646
		1647	# if your FREEZE methods return no values, you need this replace first:
		1648	$json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[\s*\]/[$1]/gx;
		1649
		1650	# this works for non-empty constructor arg lists:
		1651	$json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[/[$1,/gx;
		1652
		1653	And here is a less readable version that is easy to adapt to other
		1654	languages:
		1655
		1656	$json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/[$1,/g;
		1657
		1658	Here is an ECMAScript version (same regex):
		1659
		1660	json = json.replace (/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/g, "[$1,");
		1661
		1662	Since this syntax converts to standard JSON arrays, it might be hard to
		1663	distinguish serialised objects from normal arrays. You can prepend a
		1664	"magic number" as first array element to reduce chances of a collision:
		1665
		1666	$json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1667
		1668	And after decoding the JSON text, you could walk the data
		1669	structure looking for arrays with a first element of
		1670	C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>.
		1671
		1672	The same approach can be used to create the tagged format with another
		1673	encoder. First, you create an array with the magic string as first member,
		1674	the classname as second, and constructor arguments last, encode it as part
		1675	of your JSON structure, and then:
		1676
		1677	$json =~ s/\[\s*"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s*,\s*("([^\\":,]+|\\.|::)*")\s*,/($1)[/g;
		1678
		1679	Again, this has some limitations - the magic string must not be encoded
		1680	with character escapes, and the constructor arguments must be non-empty.
		1681
		1682
		1683	=head1 RFC7159
		1684
		1685	Since this module was written, Google has written a new JSON RFC, RFC 7159
		1686	(and RFC7158). Unfortunately, this RFC breaks compatibility with both the
		1687	original JSON specification on www.json.org and RFC4627.
		1688
		1689	As far as I can see, you can get partial compatibility when parsing by
		1690	using C<< ->allow_nonref >>. However, consider the security implications
		1691	of doing so.
		1692
		1693	I haven't decided yet when to break compatibility with RFC4627 by default
		1694	(and potentially leave applications insecure) and change the default to
		1695	follow RFC7159, but application authors are well advised to call C<<
		1696	->allow_nonref(0) >> even if this is the current default, if they cannot
		1697	handle non-reference values, in preparation for the day when the default
		1698	will change.
		1699
		1700
1186	=head1 THREADS	1701	=head1 (I-)THREADS
1187		1702
1188	This module is I<not> guaranteed to be thread safe and there are no	1703	This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe
1189	plans to change this until Perl gets thread support (as opposed to the	1704	and there are no plans to change this. Note that perl's builtin so-called
1190	horribly slow so-called "threads" which are simply slow and bloated	1705	theeads/ithreads are officially deprecated and should not be used.
1191	process simulations - use fork, its I<much> faster, cheaper, better).
1192		1706
1193	(It might actually work, but you have been warned).	1707
		1708	=head1 THE PERILS OF SETLOCALE
		1709
		1710	Sometimes people avoid the Perl locale support and directly call the
		1711	system's setlocale function with C<LC_ALL>.
		1712
		1713	This breaks both perl and modules such as JSON::XS, as stringification of
		1714	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1715	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1716	perl to stringify numbers).
		1717
		1718	The solution is simple: don't call C<setlocale>, or use it for only those
		1719	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1720
		1721	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1722	actually needs it (avoiding stringification of numbers), and restore it
		1723	afterwards.
1194		1724
1195		1725
1196	=head1 BUGS	1726	=head1 BUGS
1197		1727
1198	While the goal of this module is to be correct, that unfortunately does	1728	While the goal of this module is to be correct, that unfortunately does
1199	not mean its bug-free, only that I think its design is bug-free. It is	1729	not mean it's bug-free, only that I think its design is bug-free. If you
1200	still relatively early in its development. If you keep reporting bugs they	1730	keep reporting bugs they will be fixed swiftly, though.
1201	will be fixed swiftly, though.
1202		1731
1203	Please refrain from using rt.cpan.org or any other bug reporting	1732	Please refrain from using rt.cpan.org or any other bug reporting
1204	service. I put the contact address into my modules for a reason.	1733	service. I put the contact address into my modules for a reason.
1205		1734
1206	=cut	1735	=cut
1207		1736
1208	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1737	BEGIN {
1209	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1738	*true = \$Types::Serialiser::true;
		1739	*true = \&Types::Serialiser::true;
		1740	*false = \$Types::Serialiser::false;
		1741	*false = \&Types::Serialiser::false;
		1742	*is_bool = \&Types::Serialiser::is_bool;
1210		1743
1211	sub true() { $true }	1744	*JSON::XS::Boolean:: = *Types::Serialiser::Boolean::;
1212	sub false() { $false }
1213
1214	sub is_bool($) {
1215	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1216	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1217	}	1745	}
1218		1746
1219	XSLoader::load "JSON::XS", $VERSION;	1747	XSLoader::load "JSON::XS", $VERSION;
1220		1748
1221	package JSON::XS::Boolean;	1749	=head1 SEE ALSO
1222		1750
1223	use overload	1751	The F<json_xs> command line utility for quick experiments.
1224	"0+" => sub { ${$_[0]} },
1225	"++" => sub { $_[0] = ${$_[0]} + 1 },
1226	"--" => sub { $_[0] = ${$_[0]} - 1 },
1227	fallback => 1;
1228
1229	1;
1230		1752
1231	=head1 AUTHOR	1753	=head1 AUTHOR
1232		1754
1233	Marc Lehmann <schmorp@schmorp.de>	1755	Marc Lehmann <schmorp@schmorp.de>
1234	http://home.schmorp.de/	1756	http://home.schmorp.de/
1235		1757
1236	=cut	1758	=cut
1237		1759
		1760	1
		1761

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